Transfer sheet and composition therefor



United States 3,020,170 TRANSFER SHEET AND COMPOSITION THEREFOR Norman Macaulay, Touawanda, N .Y., assignor to Moore Business Forms, Inc., Niagara Falls, N.Y., a corporation of Delaware No Drawing. Filed Oct. 12, 1960, Ser. No. 62,106

. 22 Claims. (Cl. 117-361) Transfer Coating t Marking Fluid Dispersed in Cyclized Rubber Resin Substrate Few fields have been subjected to such intense investigative scrutiny as that of pressure-sensitive transfer materials, sometimes alsoknown as copy or manifold mate rials but more generally referred to by the more prosaic name carbon paper. In its original form from which the name was derived, carbon paper consists of a sheet of tissue or other suitable form of paper coated on one side with a soft, waxy, opaque composition usually containing a high portion of waxy and/or oily constituents along with dark colored pigments, ordinarily finely divided carbon, and other fillers which gave the composition its color and to some extent at least, its texture or body as well. When such a sheet is arranged with its coated face in contact with an underlying duplicate sheet and its opposite face in contact with a superposed original record sheet and marking pressure is applied to the original sheet, by writing or typing, to record information thereon, a portion of the coating in the areas to which pressure was applied and corresponding to the recorded information becomes detached from the body of the coat ing and adhered to the duplicate sheet, transferring there-' to an exact record of the information marked on the original. The very nature of this procedure'required that the coating compositionbe of low tensile strength or soft consistency so that the tendency of the body of the coating to cohere was less than the-tendency of the co ating to adhere under pressure to an adjacent sheet with which it was in contact.

While carbon paper in its original form has been a highly valuable,indeed almost indispensible, aid in the task of maintaining records by both government and ini Thus, it tended to transfer atent O ing permanent copies of necessary records.

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stick together, especially under the combination of high temperature and humidity such as experienced on many summer days, with the result that a single sheet could be removed from the pile only with considerable difliculty.

The demand by governmental agencies for an ever increasing degree of record duplication as well as a growing emphasis by industry upon more widespread dissemination of information within and between individual departments of an organization has given added impetus to the search for a more serviceable medium for provid- At the beginning, this search tended to'be concentrated on the more obvious approach of counteracting or eliminating the undesirable properties of the carbon-type coating compositions by suitable modification or improvement thereof and there have thus been proposed numerous additives for such compositions as well as various types of barrier coats or layers to protect the actual transfer composition except under actual marking pressure. most part, these proposals met with little commercial recognition and, more recently, efforts have centered on the more basic or radical approach of devising an en tirely new transfer principle. By and large, the proposals along this line have contemplated the use of a solvent type composition, that is, a transfer composition adapted to be dissolved in a solvent, applied as a thin coating to the base'sheet, and subjected to treatment to remove the solvent, as opposed to the so-called hot melt compositions, of which the conventional carbon coating composition is a prime example, wherein the composition of normally semi-solid consistency was placed ing, handling and-applying the composition to paper. In

' protect the transfer fluid except under the impact of' marking or unintentional circumstances, including its own setting, carbon paper is peculiarly subject to blocking,

the term applied to the proclivity of adjacent sheets to addition, the deposition of the coating from a solution makes possible the use of materials which dry to a tougher, more durable state, and is, furthermore, at leastthe first step towards the development of a coating capable of prolonged use without loss of transfer efficiency. By its very nature, carbon paper must lose, dur ing transfer, some of its coating, which, being semi-solid cannot heal itself. a h

In general, most solvent systems suggested to dateshare the common principle of a transfer or marking fluid dispersed or otherwise uniformly distributed in a solvent solution of a film-forming substancewhich, when applied as a coating to the base sheet and freed of solvent, results in a continuous film of the film-forming substance having the transfer fluids included or entrained therein. The continuous film, of course, served to enclose and marking pressure, which ruptures or squeezes the film causing the transfer fluid to be exuded therefrom onto duplicate sheets in contact therewith in the localized areas corresponding to the zones to which marking pressure was applied. Most of the specific proposals for such systems have been concerned with the reaction mechanism of the marking fluid, it having been suggested,

. for example, that the transfer fluid contain as the colorant component certain colorless dye intermediates which assume color only when brought into reactive contact with selected materials provided for this purpose on the contacting surface of the duplicating sheet or else provided as a distinct additional ingredient of the transfer coating and maintained out of contact with the color forming intermediate by the continuous film except under the im pact of marking pressure, as well as to the state in which the marking fluid exists Within the continuous film, other suggestions involving the application to the transfer fluid of recently developed encapsulation techniques to pro- For they vide the fluid inclusions with distinct shell-like walls. In particular, concentrated attention has been focused on devising specific combinations of chemical compounds adapted to react on contact to produce a visible impression.

While the solvent transfer systems of the various types just described may, from an overall point of view, be considered an improvement upon the carbon system, they have not as yet been perfected to the point of providing a complete answer to the diverse requirements of a high quality transfer material. For instance, in the transfer systems utilizing two sheets, one sheet carrying a coating containing the colorless intermediate and the other the color-developing agent for the intermediate, it is frequently necessary to provide a rather high degree of dilution of the intermediate by a color carrier fluid to insure exudation or transfer of the intermediate in suflicient amounts to be rapidly absorbed by the duplicate sheet with concommitant rapid color development. However, such high degree of dilution naturally tended to increase the likelihood of undesirable bleeding of the fluid onto an underlying duplicate sheet when stacked in alternation therewith, increased the time required for the developed image to dry so that the image was more easily smudged or smeared if handled'too soon, and led to less sharp images due to the propensity of the fluid to spread or wick outside the immediate image area.

Another area in which present-day solvent type transfer systems have failed to afford a significant improvement over conventional carbon paper is that of multiuse transfer sheets. For many purposes, it is highly desirable, if not essential, that the transfer sheet give a readily discernible duplicate image when used over and over again for numerous transfer operations with fresh original and duplicate sheets. One outstanding example of such a case is in connection with autographic registers in which one or more transfer sheets is interleaved with a consecutive series of original and duplicate record sheets, successive sets of record sheets being brought into position for the recording of data incidental to a sales transaction, for example, as the previous set is removed. Current commercial versions of solvent-type transfer materials begin to show a loss in quality of transfer image impression after one or two dozen transfer operations, which loss is a very definite disadvantage since frequent replacement of the sheets is both annoying and expensive. Even under more commonplace circumstances of use, as for typical office purposes, the short life of transfer materials, both of the conventional and newer types, is a well acknowledged fact. a 1

In contrast to the extensive research that has been carried out relative to the composition and state or form of the transfer fluid, surprisingly little Work has been done toward improving the characteristics: of the continuous film of the solvent type system and it is believed that much of the weaknesses in currently available materials of this type can be attributed to this mis-direction of emphasis. Thus, in as recent patent as 2,885,302, the continuous film of the system was still constituted by such natural film-forming substances as gelatin or casein, both of which are suggested for the same purpose in U.S. Patent 2,374,862, one of the basic patents in this art. Having come to the realization that the film-forming substance is perhaps the most critical constituent of a solvent-type transfer system and after a comprehensive study of a large selection of such substances, both natural and synthetic, l have discovered that one limited category ing agent. I have, for instance, by following the principles of the present invention, obtained a transfer material which yielded 400 separate identical impressions from the same area of the carbon sheet With very little loss in the distinctiveness or quality of impression when tested by the conventional method in an automatic autographic writing machine.

The principal object of the present invention is therefore an improved transfer material of the solvent type utilizing as the film forming substance a cyclized rubber resin which confers to the transfer coating exceptional toughness and durability combined with the required degree of elasticity, rendering the transfer material resistant to smudging and bleeding of the transfer fluid either upon the hands of the user or contacting surfaces and to loss of impression quality during repeated use.

Another object of the invention is a pressure-sensitive record material having an extremely long useful life as compared to previously known similar materials without detriment to the other qualities desirable in such materials.

A further object of the invention is a transfer material having on one surface thereof a transfer coating including as essential components a continuous film of a cyclized rubber resin and a transfer or marking fluid distributed uniformly throughout .the film in the form of finely divided liquid globules, the marking fluid being comprised at least mainly by a color-providing or colorforrning agent and a liquid color carrier therefor, in which the proportion of marking fluid to resin as well as the proportion of color agent to color carrier are maintained within certain well defined limits to prevent unintentional release of the marking fluid to the transfer coating while providing a good quality of impression during repeated use.

The invention also comprehends the coating composition which gives to the transfer material its desirable qualities and characteristics.

These and other objects and advantages of the invention will be readily comprehensible from the following detailed description.

In essence, the transfer material of the present invention takes the form of a base sheet carrying on at least one face thereof a layer, whose thickness is dependent upon Whether the sheet is to be adapted for multiple or limited use, of a cyclized rubber resin, the resin extending as a continuous film over that area of the sheet which is to be served for transfer purposes, and a marking fluid dispersed or otherwise distributed throughout the resin film in the form of extremely fine globules or similar small fluid inclusions in sufiicient proportion to the weight of the resin tobe exuded or otherwise released therefrom when the resin film is rupturedunder marking pressure.

The marking fluid has for its basic constituents a colorant, which may be either colored in itself or else such as to develop or acquire color under the intended conditions of use, and a liquid vehicle or carrier for the colorant which is a non-solvent for cyclized rubber resin.

7 The concentration of the colorant in the marking fluid is sufiicient to produce a distinct durable impression upon transfer to a duplicate sheet but insufi'icient to cause the impression to be subject to smudging, smearing, or staining when brought into frictional contact with other surfaces or the hands of the user. Other materials may be present in minor amounts, such as a plasticizer for the resin to increase the flexibility 'and/ or elasticity of the transfer coating. Dispersion of the marking fluid is preferably obtained by emulsifying the same in a solution of the resin component in a volatile solvent which is immiscible with the vehicle of the marking fluid as well as a non-solvent for the colorant. The colorant may be a dyestuff or dyestuffinterrnediate in which case it is or dinarily dissolved in the vehicle, the vehicle being selected with this function in mind, or the colorant may instead be in the form of a finely divided solid, such as a pigment or the like, distributed uniformly throughout the vehicle. Certain vehicles have been found to be of outstanding effectiveness although others can be utilized with somewhat lesser results dependent upon the colorant to be used. In any case, the vehicle must be a high boiling organic solvent which is liquid at normal temperatures, incapable of dissolving the resin or mixing with the resin solvent, and a good solvent or suspending agent for the colorant.

The most important feature of the present invention by which it is distinguished from the prior art is the use of a cyclized rubber resin as the essential film-forming agent of the transfer composition. These resins are the selfcondensation products of natural rubber and are obtained by subjecting rubber, usually in the form of a solution in an appropriate rubber solvent, in the presence of a condensation catalyst to heating at temperatures near the solvent boiling point for a period of several hours, say 612 hours, and until the viscosity of the rubber solution has been reduced to a predetermined end point. Condensation catalysts suitable for this purpose include the halides of amphoteric metals, such as tin, Zinc and the like, tin tetrachloride being a good example; the halogenated acids of tin, such as hydrated chlorostanic acid; as well as boron trifluoride and fluoroboric acid or the like. When the reaction has reached the desired end point, the condensation product may be recovered by quenching with water preferably in suflicient amounts to form an emulsion with the reaction product constituting the discontinuous phase, followed by distillation to remove the water and the solvent, leaving the product in the form of finely divided particles; or by reformation with acetone or alcohol. One procedure for preparing cyclized rubber resins is disclosed in greater detail in US. Patent 2,052,391.

The product of this reaction is a highly condensed aromatic ring system free of halogen as well as many of the impurities normally accompanying natural rubber, which system apparently results from the formation of rings and cross links through the double bonds of the natural rubber molecule. No accepted structural formula for the produce has as yet been established. The cyclized material has a relatively low degree of unsaturation as compared to natural rubber, the iodine value thereof being within the range of 75-95, and is also of much reduced molecular weight, averaging approximately 5,000- 10,000, as compared to several hundred thousand for natural rubber. For other significant properties, the following values have been established: specific gravity 1.00-1.05, refractive index at 25 C.1.54, acid value -1, and saponification value zero.

Cyclized natural rubber resins are presently available from two commercial sources, the Goodyear Tire and Rubber Company of Akron, Ohio and Alkydol Laboratories Division of Reichhold Chemicals, Inc. of Cicero, Illinois, under the trade designations of Pliolite NR and Alpex, respectively. Several grades are available from each of these sources, apparently difiering mainly in the time of reaction to achieve a somewhat different end point viscosity and range of softening temperatures as Well. As far as I am able to determine, the variations in these grades appear-to have little or no effect on their suitability for use in the present invention. For ease in handling and dissolving, the product is preferably obtained in the form of a powdered or granulated solid, either unmilled or milled and granulated or as a previously formed solution.

Very recently, each of the above manufacturers have made available a cyclized version of a synthetic rubber per se or in admixture with natural rubber. Although experiments with these new derivatives is incomplete, due to the unavailability of commercial quantities, preliminary indications are that the Alpex derivative sold under the designation Alpex 841, is equivalent to the natural rubber product, but that the Goodyear derivatives, sold under the designations of Pliolite VT and VT L and believed to be based on a vinyl toluene polymer, is inferior for present purposes, especially with regard to stability of the transfer composition emulsion. In 'vieW of these conflicting results, cyclized forms of synthetic materials comparable to natural rubber should be considered on an individual basis as they become available.

As indicated by comparative experiments included in the examples appearing hereinafter, the presence of a plasticizer for the cyclized resin is not critical Equally good results have been obtained where the resin was utilized alone as where minor amounts of a plasticizer were included, at least where the comparison was made While the transfer sheets were fairly fresh. There is some possibility that, after long periods of time,-an unplasticized film may exhibit some tendency to become more brittle or lose its continuity. Consequently, if the sheet is to be stored for a number of months or longer prior to use, the presence of a plasticizer may be desirable. In general, plasticized films are more flexible with less risk of cracking or breaking of the film and may be preferred for this reason, among others. Furthermore, there is a cost advantage in replacing some of the resin with the less expensive plasticizer; therefore, the use of as much plasticizer as can be reasonably tolerated by the system is more economical, as a practical matter. By and large, any plasticizer that is soluble in hydrocarbon type oil or solvent oil qualifies for use in the present system, examples of suitable plasticizers being the well known ester-type materials, such as dibutyl maleate, dioctyl phthalate, dibutyl phthalate, di (2-ethyl hexyl) maleate; the chlorinated hydrocarbons, hydrocarbonaceous substances such as mineral oil, vegetable Waxes, hydrocarbon Waxes, mineral waxes, synthetic Waxes, et cetera. The plasticizer art is quite highly developed at the present time and the selection of suitable materials from among the wide variety available is well within the capabilities of the resin chemist. The amount of the plasticizer iricorporated into the system should not exceed about 20% based upon the Weight of the cyclized rubber resin as more than this amount tends to make the film excessively soft and/or sticky. Where the plasticizer is included, a like quantity of the resin is omitted in order that the total amount of film-forming materials, constituted at least essentially by the cyclized resin and plasticizer, will remain the same at any given ratio relative to the marking fluid. Obviously, the minimum amount of plasticizer capable of imparting a beneficial elfect may vary to some extent with each such material, although, as a rule, about 25% will be found to represent approximately the level at which a practical effect appears.

To place the cyclized resin in the form suitable for addition of the marking fluid, the resin is dissolved in a solvent. These resins are known to be soluble in virtually any rubber solvent but some of these solvents, in particular those of the aromatic type either are miscible with the fluid vehicle of the marking fluid or are possible solvents for some of the colorants contemplated for use in the system. Consequently, the resin solvent must be selected not only fromthe point of view of goodsolvent action for the resin itself, but for relative insolubility with other components of the system. As a practical matter, aliphatic hydrocarbons, such as various thinners derived from petroleum, will be found to be the most suitable. For example, the aliphatic naphthas having a speclfic gravity range (60/60 F.) of about 0.740-0.806, a boiling point range (I.B.P.) of about 205 F.-413 F. (dry point 255 F.477 F.), and a flash point range (T.C.C.) of about 25 F.-l75 F. have been found to possess the requisite insolubility for the marking fluid in the case of virtually all of the particular fluid vehicles hereinafter enumerated. These are sold under various proprietary designations, such' as Troluoil, the registered trademark of Anderson-Pritchard Oil Corp. for its sol vent having a sp. gr. of 0.741 and a flash point of 25 F. and Lacolene, V.M. & P., Kwik-Dri, etc., all tradenames of Ashland Oil and Refining Co., Bronoco Solvents and Chemicals Division, for various solvents having characteristics within the ranges mentioned. On the other hand, toluene and xylene, examples of the aromatic type, dissolve many of the fluid vehicles, except the lower polyethylene glycols, e.g. triethylene glycol, and their thio derivations, e.g. thiodiethylene glycol. Hence, while hydrocarbon solvents other than the alkane variety can be employed in the invention, some experimentation may be necessary to arrive at a suitable immiscible system. Obviously, as the resin solvent is to be removed after the transfer composition has been applied to the base sheet, a further requisite of the solvent must be relative ease of evaporation within the range of temperatures, typically 30-100 C., at which the coating is to be dried. Drying at temperatures in excess of the flash point of the resin solvent is possible due to the absence of an open flame which might ignite the solvent vapors, the drying being accomplished by hot air or the like as is well known in the art. If the Wet film is to be exposed to an open flame, some precautions would obviously be necessary to avoid flashing.

The amount of solvent that can be used to dissolve the resin is not critical as it is absent, due to prior evaporation, from the final coating and has no effect on its transfer properties. in fact, the main role of this solvent is to adjust the volume of the resin at the time of introduction of the marking fluid to give an excess over the volume of marking fluid, whereby the resin will constitute the continuous and the marking fluid the dispersed phase of the system. With this in mind, the quantity of solvent may vary from about 30-60% of the Weight of the overall coating composition, i.e. prior to drying, dependent upon the proportion of resin that is present.

The marking fluid of the composition, that is the fluid which is released from the transfer sheet during the transferring operation to form an impression on the duplicate sheet, consists of only two basic or essential components, namely the color-providing or color-forming compound, referred to broadly herein as colorant, plus the fluid vehicle therefor. Since the present invention is founded upon principles other than the nature of the colorant substance and/or the mechanism by which color is developed, in distinct contrast to a great deal of the recent activity in this field, it appears to be largely independent of particular colorants and the utilization of almost any of the wide variety of coloration modes andtechniques known to the prior art is possible. Where the transfer sheet is to be of the type which might be characterized as self-contained, which is to say that the transfer sheet is adapted for use with conventional paper as the duplicate record and includes all of the components necessary for a transfer operation without resort to specially prepared adjuncts, the colorant may be, and preferably is, a suitable dye which is soluble with the selected fluid vehicle. A wide selection of dyes is available, such as those of the diand tri-aryl-methane classes, for example, Malachite Green, Crystal Violet, Victoria Blue, and Auramine; spirit soluble dyes as are often used for hectographic purposes, such as Spirit Soluble Blue; and dyes of the class disclosed in US. Patent 1,674,128 and 1,800,300 which are water insoluble salts of organic bases with organic dyes having sulfonic acid groups, as for instance Cl. Acid Blue #1 (Cl. No. 420,405) and Cl. Acid Green #3 (Cl. No. 420,850). It is neither practicable nor possible within the limit of the present disclosure to provide an exhaustive list of the myriad dyestuffs having the possible value in the invention, since in addition to those classes mentioned, other broad classes, such as the azo, indigoid, and thioindigoid, anthraquinone, acridine, azine, oxazine, and thiazine dyes, have potential utility as the colorant.

For most purposes the more suitable types of dyes will be those having deep, brilliant coloration, although lighter shades can be employed if the background color of the duplicate sheet is appropriately selected to give good contrast. Again, it is ordinarily preferred to employ a water insoluble dyestuff for the very practical reason that where the hands of the user are moist, as from perspiration, water insoluble materials possess a lesser tendency to smear or stain when the duplicate sheet is handled, as is often necessary in the course of filing or the like. The identification of specific dyes is not to be construed as an implication that only a single dye may be employed as the colorant. To the contrary, it is common practice in the art to compound two or more dyes into a single preparation and thereby obtain a particularly satisfactory shade or a balancing of other valuable characteristics, and many commercially available dyes are compounded in this manner. 1

in lieu of the soluble dyes just mentioned, there may be employed solid colorants which are dispersed in the marking fluid, These soluble colorants will ordinarily be constituted by pigments and, again, a wide range of materials is available. Examples of suitable pigments are the carbon blacks, iron blues, alkali blues, phthalocyanines, cadmium reds, ultrarnarine blues, phosphoand molybdo-tungstic acids, laked colors, and so on.

In addition to the self-contained transfer material, the concept of the invention is also applicable to two-sheet transfer systems, in which one'sheet contains as the colorant of the transfer composition a colorless intermediate form of a dyestnff and the other sheet is coated or otherwise treated with a chemical compound which is adapted to react with the colorless intermediate when brought into contact therewith to convert the intermediate to colored form.

Among the usable color-forming intermediates are the following classes: stabilized diazonium salts; the carbinol, leuco, and ether derivatives of triaryl and diaryl methane dyes; and acid esters of leuco. indigoid and thioindigoid dyes. As specific examples of these classes of colorless intermediates may be mentioned, the butyl ethers of Methyl Violet 2B, Methyl Violet 10B, Magenta, Malachite Green A, N-acetyl Auramine and leucoauramines, the lactones of Crystal Violet and Malachite Green and so on. The reaction mechanism of these dyes may be of various types, one type being that disclosed in British Patent 757,136. Here, the dyestuff is of such a chemical character that it loses its color upon neutralization with alkali but reverts to its former colored condition when rte-acidified. Examples of dyes behaving in this fashion are Malachite Green and Crystal Violet, which, when brought into contact with a base are converted to their leuco base or carbinol form but when the effect of the base is eliminated, as by neutralization with an acid, again take on color. To prepare a transfer system functioning in this manner, enough of an alkali, such as sodium carbonate, potassium carbonate, a quaternary amine, etc, is mixed in with the colored dye to neutralize the same, and the mixture incorporated as a colorant into the marking fluid of the transfer composition and coated onto thetransfer sheet. For association with this sheet, the duplicate sheet is especially prepared to carry on its front surface an excess of an acid adapted to react with the colorless intermediate as the same is released onto the duplicate sheet in the course of the transfer operation, examples of suitable acids being tannic acid, gallic acid, citric acid, boric acid, and so on, as well as mineral acids when capable of effective use at sufficiently low concentrations as to be harmless. Alternatively, it is known from US. Patent 2,548,366, that the color dyestufl may be in the form of an aromatic compound convertible through an electron acceptor-donor surface chemical reaction to a more highly polarized conjugated formpossessing distinctive color, which is included as the colorant of the transfer composition, the face of the duplicate sheet being coated with an inorganic absorbent reactant capable of functioning as an electron acceptor when brought into contact with the selected colorless intermediate, examples of suitable inorganic 9 absorbents being attapulgite, halloysite, magnesium trisilicate, among others. In either of these two-sheet systems, the position of the colorless intermediate and the color developing reactant therefor, may, of course, be reversed, the reactant occurring on the transfer sheet and the colorless intermediate on the duplicate sheet.

A further system known from U.S. Patent 2,505,470, among others, is, in effect, an adaptation of the twosheet transfer principle to a self-contained transfer sheet. This is accomplished by incorporating into the marking fluid both the colorless intermediate and the color-developing reactant therefor under such conditions that they are maintained separate from one another until the occurrence of a transfer operation.

Similar to the soluble dyes and for the same reason, it is preferred that the solid colorant or two-component colorant have a relatively low solubility in water and be such as to provide distinctive brilliant coloration against the selected background of the duplicate sheet.

As might not be wholly unexpected, the concentration of colorant in the marking fluid has been found to bear a rather significant relationship to the intensity and the general quality of the impression produced on the duplicate sheet. In general, a range of about 10% to about 30% of colorant based on the total weight of the marking fluid has been found to represent the approximate maximum permissible limits of colorant concentration, dependent to some extent on both the inherent brilliance of the colorant as well as to the overall fluid content of the ultimate dried transfer coating. Below about 10%, e.g. at about the concentration of colorant in the marking fluid becomes so low as to yield impressions of poor quality. In addition, very dilute marking fluids tend to be especially prone to bleeding and smudging. By way of explanation, the term bleeding is used to describe diffusion or leakage of the marking fluid from the transfer film under static conditions, i.e., seepage of the fluid through the base or backing sheet or onto a copy sheet in stationary contact with the transfer sheet in the absence of marking pressure. The term smudging, on the other hand, has reference to the spreading or smearing of the impression image when rubbed or scuffed. Above 30%, e.g. at about 35%, colorant concentration, the marking fluid becomes extremely thick or viscous to the point the exudation from the transfer film under normal or reasonable marking pressure does not readily' occur and impression quality suffers.

One particularly interesting property of the marking fluid is the tendency for the transfer impression or writeoflf to be adjusted or compensated for automatically with respect to variations in colorant concentration. This follows from the fact that the amount of marking fluid exuded or otherwise released from the transfer coating under marking pressure is influenced mainly by the viscosity of the marking fluid, which viscosity is, in turn, determined for a given colorant vehicle by the concentration of dye. As a consequence, at low concentrations of colorant in the marking fluid, While the color intensity of the fluid per se may be low, the viscosity of the resultant solution is also low and more of the fluid will tend to be released under a given pressure. On the other hand, at high dye concentrations, the viscosity of the resultant solution is equally high so that less of the marking fluid will be released upon the transfer but the amount released will have a greater color intensity due to the relatively greater amount of dye that it contains. However, this feature of self-condensation of write-off intensity has its practical limits. At very low color concentration, the durability of the image becomes poor to the point of unacceptability despite a satisfactory intensity level and, conversely, at very high concentrations the solution viscosity becomes so great that the amount of marking fluid released from the coating under normal pressure becomes virtually negligible with concommitant poor quality of transfer impressions.

For some color-ants, the lower limit of 10% as indicated above produces results which tend to be on the marginal side, and, for this reason, a somewhat narrower range, say from about 15% to 20% to about 25% to 30%, again based on the marking fluid weight, is a more optimum range and is preferred. The influence of colorant concentration on impression quality is illustrated hereinafter in Table I in the examples of the invention, utiliz ing crystal violet as the colorant substance. As revealed by this table, for this particular dye, the intensity of write-off is of marginal acceptability below about 25% concentration while the durability of the impression exhibits a distinct improvement at approximately the 20% level. Obviously, the optimum concentration may vary from colorant to colorant.

The essential function of the colorant vehicle is, of course, that of serving as that of a convenient carrier having properties compatible with the other components of the transfer system of the invention and capable of placing the colorant in such a condition as to be effectively displaced from the transfer coating to the surface of the duplicate sheet during a transfer. operation. To this end, there are certain distinct requirements imposed on the vehicle. To begin with, it must be a'free-flowing liquid, as opposed to a solid or semi-solid, and remain fluid in consistency throughout a broad range of operating temperatures, say from at least as low as 10 C., and preferably down to 30 C., to at least C., and preferably C. Obviously, this means that the colorant vehicle must have a freezing point consistent with the temperatures just specified and a boiling point in excess of 100 C. The colorant vehicle, of course, is not evolved during drying but remains a part of the transfer film on the sheet as actually used by the consumer. To minimize the risk of flammability in the event the film be brought during use into close proximity with flame, for instance, a lighted match or cigarette," the vehicle should have a high flash point or, more preferably, be non-inflammable, as is true of most, if not all, of the vehicles'specifically identified herein. This is largely a pre caution, in view of the low vapor pressure of the vehicles, next to be discussed, and, by and large, fluids having a flash point above 100 F. are generally) satisfactory in this respect. As a corollary to the high boiling point of useful colorant vehicles, the vapor pressure thereof should be quite low and preferably less than 0.01 mm. of mercury at about 25 C. An additional reason for this property is to prolong the shelf life of the transfer material and, at most, the volatility of the vehicle should be such that not more than about 10% of its weight should be lost through evaporation from the coating over a period of 2-3 years of normal storage.

A further requisite of suitable colorant vehicles is that they have good solvent action for the dye or colorless dye intermediate, where of the soluble type, or, similarly, a good suspending action for the pigment or other insoluble colorant to be employed. On the other hand, satisfactory colorant vehicles must necessarily have a low order of solubility and/or miscibility, preferably substantially zero, in both the cyclized rubber resin and the resin solvent. As will be subsequently explained more fully, the transfer composition of the invention is an emulsion system which, by definition, necessitates that the resin solvent and the colorant vehicle be substantially immiscible with one another. In like manner, to preserve the discontinuityof the marking or transfer fluid within the continuous resin film after the composition is applied to the base sheet'and the resin solvent removed, the colorant vehicle must be free of any-tendency to exert a solvent action upon the resin as might result in softening of the resin film and loss of the marking fluid.

The suitability of particular solvents meeting these general requirements is, to some extent at least, dictated by the choice of the particular colorant with which it is to be associated but, from a general point of view, it can be stated that high-boiling organic solvents having relatively high oxygen content, especially in the form of at least one and preferably two hydroxyl groups, and equivalent substances will be found to give more or less acceptable results. Within this class may be mentioned the simple alkane diols, such as ethanediol, propanediol, butanediol, pentanediol as Well as those higher homologues which are liquid at normal working temperatures; the polyalkylene glycols and their corresponding thioether and lower alkoxy derivatives, such as diethylene glycol, triethylene glycol, tripropylene glycol, thiodiethylene glycol, ethoxytriglycol, and the like, having a molecular Weight from about 200-600 or otherwise such as to be liquid at normal temperatures.

For at least those systems based on a dye or colorless dye intermediate, two specific organic solvents meeting the previously defined general requirements have been found to possess particularly outstanding characteristics as colorant vehicles. The first of these materials is a liquid polyepichlorohydrin having an approximate molecular weight of 450 and containing two terminal hydroxyl groups per molecule, which is sold under the trade name of Polyglycol 166-450, by Dow Chemical Company. The other is a mixture of orthoand para-N-ethyl-toluene sulfonamide, sold under the trade name of Santicizer 8 by Monsanto Chemical Company. These two materials have the apparently unique property of possessing both polar and non-polar characteristics in that they are both immiscible with the suitable resin solvents and insoluble in water. In addition, theyare both liquid, at normal temperatures and have excellent solubility for the preferred classes of dyes and colorless dye intermediates. While other organic compounds this peculiar combination of characteristics may exist, a reasonably comprehensive examination of thefield has failed to bring them to light. For instance, unsubstituted mixed toluene sulfonamides and the N-ethyl para-compound alone, while being otherwise useful, in all probability, are solid at room temperature. However, if desired, for reasons of expense or convenience, up to 50% by weight of either of these materials may be replaced with a lower alkyl phthalyl, lower alkyl glycolate, such as butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, and methyl phthayl methyl glycolate, sold under the trade names of Santicizer 3-16, E-IS and M-17, respectively, by Monsanto Chemical Company. Either of these materials alone possesses insufficient solvent power for the preferred dyes or colorless dye intermediates to give optimum results. By lower aikyl is meant from 1 to about 5 carbon atoms.

From what has been said with reference to Polyglycol l66450 and Santicizer 8, it will have been. understood that these two materials are especially highly regarded for present purposes, and indeed, this is true. However, where the circumstances are such that a somewhat less optimum transfer system can be used satisfactorily, as for example where a moderate amount of water solubility for the colorant vehicle can be tolerated, or the particular colorant selected does not require so critical a combination of characteristics in the vehicle, other vehicles from the variousclasses already mentioned may be substituted with usually acceptable performance.

My experiments indicate that the ratio of the amount of marking fluid to the amount of resin in the ultimate transfer coating distinctly affects the performance of the sheets in actual use. Unless the quantity of marking fluid phase distributed throughout the transfer layer equals at least about 25% by weight of the amount of the cyclized rubber resin phase on a dry basis, i.e. exclusive of the resin solvent, insufficient marking fluid is present to produce even a weak impression on transfer. In other words, where the amount of resin phase is more than about three times the amount of the marking fluid, so great an excess of film-forming materials is present that virtually no release of the fluid occurs under normal marking pres sure. Where the proportions are reversed, that is, the amount of resin phase constitutes less than about onethird of the amount of the marking fluid, then so great an excess of marking fluid exists that the resin film becomes insubstantial and unable to contain the fluid, which therefore begins to bleed excessively onto the duplicate sheet, causing staining, smudging, as well as loss of definition in the transfer impression. Within this broad range of 3l:l3 exists a somewhat narrower preferred range wherein optimum performance is usually obtained, this preferred range being from approximately a ratio of about /55 and about 70/30 of the weight of a marking fluid to the weight of the film-formers. For a more dramatic demonstration of the effect on performance of variation in the content of marking fluid relative to the resin component, reference may be made to Table II of the examples.

In view of the rather wide permissible variations in the amounts of the various major components of the transfer system of the present invention, it is rather diflicult to describe the composition in terms of a range of percentages by weight of each major component, especially Where the resin solvent is considered. However, it appears that the following r-anges are more or less accurate: total weight of film-forming materials or solids in the continuous phase, about l0-52.5%; total Weight of marking fluid or dispersed phase, 10-52.5%; and weight solvent, 30-60%. Where from about 020% of the resin is replaced by a plasticizer, the ranges of these materials in the continuous phase would be about 10- 52.5% resin and about 010.5% plasticizer, exclusive of any other materials in this phase. The ranges for the dispersed phase and solvent would, of course, remain the same. The constituency of the marking fluid has already been provided.

The manufacture of the transfer composition and its application to the base sheet does not differ greatly from what has already been described in several issued pattents, in particular, 2,299,693 and 694 and 2,374,862. In general, the colorant is dissolved or suspended in the liquid vehicle therefor to produce the marking fluid which is then emulsified as the discontinuous phase With the 501m vent solution of the cyclized rubber resin. Under most conditions, the component of the system which is present in excess automatically becomes the continuous phase of an emulsion for-med therefrom, and it is normally necessary that the quantity of the resin solution be somewhat greater than that of the marking fluid. If desired, an emulsification assistant can be incorporated into the systern although good stable emulsions have been obtained without the use of such assistants. The dispersion is preferably effected with eificient, high speed mechanical devices such as a Kady Mill or a Waring Blender. It is important that a good stable emulsion or dispersion result with the discrete finely subdivided particles or inclusions of marking fluid having an average diameter within the range of about 0.1 to about 70 microns. While 70 microns represents the'maximurn permissible upper limit, it has been found that when the diameter of the marking fluid globules or inclusion exceeds about 20 microns, the transfer material may possess a tendency to become slightly dirty to the touch, the diameter of the inclusions at this value being roughly of the same order of the thickness of the coating and therefore easily broken. At the other end of the range, certain systems have been found to give satisfactory results despite the fact that a particle size undiscerni-ble at a magnification of 210 and therefore somewhat less than 0.1 micron was produced by emulsification. In general, however, 0.1 micron represents about as low a level as can be adopted for a wide range of systems without risk of some loss in sensitivity to release of marking fluid under normal impact pressure. For these reasons, a somewhat lesser range of about 0.1 to about 20 microns produces more satisfactory results and 500 sheet ream basis on a lb. paper.

cial driers operating at temperatures of the order of about The amount of the ultimate coating actually applied to the transfer record sheet is governed principally by the use for which the same is intended. It follows from what has already been stated that the principles of the invention are used to fullest advantage in connection with multipleuse sheets, that is transfer materials which are to be sold for repeated use over a fairly lengthy period. However, if desired, its novel features can be availed of to a lesser but nevertheless valuable extent with one-time or limited use transfer materials. For multiple use purposes, the weight of the coating should range from about 6 to about 12-14 pounds, with 810 pounds being preferred, while for limited use purposes a somewhat lesser amount, say from about 1 to about 6 pounds and preferably 2-4 pounds will suflice. In all cases, this weight is for a 500 sheet ream of paper, each sheet measuring x 30 inches. For such a ream, the range of 114# is equivalent to 0.00750.11 oz./ sq. ft. In addition to transfer sheets bearing the transfer coating on a single face, sheets coated on both faces can be prepared as may be desirable for certain special situations.

The description has been confined to constituents which are of basic importance to the practice of the invention. If is not, however, intended to imply that minor amounts of other materials could not be included for various reasons in the usual manner of the art. For instance, there may be added to the resin phase such substances as clays to harden the coating and/ or absorb excess marking fluid, ultraviolet absorbers to protect occluded colorless dye intermediates, or silicone fluids to reduce tack between the transfer and copy receiving sheets or blocking between stacked transfer sheets. Similarly, the marking fluid phase may contain stabilizers, such as alkalis and antioxidants for the colorless dye intermediates, thickening agents, and dye intensifiers, among others.

In order to convey a more complete understanding of the application of the invention to specific conditions and circumstances, the following working examples are provide'd, it being understood that they are intended to illustrate rather than to limit the scope of the invention. In the examples, all parts are by weight unless otherwise indicated.

EXAMPLE I 140 g. of a solution of 40 g. C.I. Acid Blue #1 (Index No. 42045) in 160 g. Polyglycol 166-450 was emulsified into a solution of 70 g. Pliolite NR resin in 250 g. Apcothinner solvent (a naphtha-type solvent from Anderson- Pritchard Oil Co., having 2 sp. gr. of 0.763 and a flash point of 52 F.) following the procedure of Example I. This emulsion was coated to a 10 lb. weight per 20 x 30- After evaporation of the solvent, the clean, non-smudgy copying sheet gave as many as 200 copies on the copy sheet with no apparent breakdown of the coating. The copies produced had excellent legibility and color intensity. Copy smudge was negligible.

152 g. of a solution of either of the dyes of Examples I and II in 160 g. Polyglycol 166-450 were emulsified intoa solution of 60 g. Pliolite NR resin and 6 g. Sun Wax 14 5512 (a close-cut paraffin wax with MJP. 155 F. from Sun Oil Co.) in 250 g. Apcothinner solvent according to the procedure of Example I. When coated on tissue to 10 lbs. per 20 x 30-500 sheet ream, an excellent multicopy paper resulted having excellent copy intensity and durability and also possessing remarkable non-bleed properties.

EXAMPLE IV A solution of 10 g. phenyl leuco auramine, a colorless dye intermediate, in 160 g. emulsified into a solution of 60 g. Pliolite NR resin, 6 g. Sun Wax 5512 and 250 g. Apco Thinner solvent according to the procedure of Example I. This emulsion was coated onto a sheet of 9 lb. carbonizing tissue to give a weight of 4 pounds on a 20" x 30"-500 sheet ream. When used with a copy sheet which had been previously treated with a dilute tannic acid solution, excellent copy reproduction was obtained in an intense blue color.

EXAMPLE V Example IV was repeated using a coating weight of 2.5 lbs. per ream. Copy reproduction was satisfactory although not quite so good as in Example 1V, particularly in the case of additional copies.

EXAMPLE VI 40 g. cyclized rubber resin (Pliolite NR, unmilled, Goodyear) and 2 g. Santicizer IH (N-cyclohexyl paratoluene sulfonamide obtained from Monsanto Chemical Co.) was dissolved in 150 g. Apco Thinner (Anderson- Prichard), 10 gm. C.I. Acid Blue #1 was dissolved in g. Polyglycol 166-450 (Dow Chemical) and this solution emulsified into the Pliolite-solvent solution with rapid agitation at room temperature. An extremely uniform and fine emulsion of particle size less than 0.5 micron diameter was produced such that the particles were barely visible at 420 magnification. When coated on paper to a dry deposit of 12 lbs. per ream (20" x 30"- 500 sheets per ream), this multi-use carbon paper gave up to 400 legible copies by writing with a #2 pencil at an autographic register machine.

EXAMPLE VII The following materials in the indicated amounts were prepared by a procedure identical to that of Example VI.

Materials: Parts Alpex 841 resin 76 Dioctyl phthalate 4 Crystal Violet dye 20 Polyglycol 166-450 vehicle Troluoil solvent 200 The performance was excellent.

EXAMPLE VIII Example VII was repeated with the following:

Materials: Parts Alpex (8 hour reaction time) 76 Dioctyl adipate plasticizer 4 Spirit Soluble Blue RBF dye 20 Santicizer 8 vehicle 12.0 Troluoil solvent 200 Again, the results were well within acceptable limits.

The following tables summarize the results of two series of experiments carried out for the indicated purpose. In each case, the ingredients were mixed in the stated proportions in the same manner as in the preceding ex amples and were coated on 15 lb. carbonizing tissue to give a coating weight of 12 lbs. (dry basis) per 500 sheet (20" x 30") ream.

Polyglycol 166450 was 1 Table I.-Efiect 0n write-ofi of increasing concentration of dye in the marking fluid Gompositionlarts by Weight Dye Gone.

in Mark- Write-ofi Durability Bleed Example Pliolite Sancticizer Crystal Polyglycol Troluoil ing Fluid,

NR 1H Violet 166-450 Solvent Percent Dye Table II.Efiect on write-0f} of increasing marking fluid content Comp0sitionParts by Weight Marking fiuid Content of Example Pliolite Santicizer Crystal Polyglycol 'lroluoil Final Sol- Writecfi Durability Bleed NR 111 Violet 166-450 Solvent vent-Free Dye Film,

Percent 76 4 1 9 113 11 76 4 2 19 125 20 76 4 4 66 159 33 76 4 6 54 176 43 None 76 4 8 72 200 Do. 76 4 16 144 3:10 67 Slight. 76 4 32 288 500 80 Definite.

In the above tables, the term durability has reference to the ability of the transfer film to stand up under repetitive writing in tests on the same area with a ballpoint pen without breaking apart or becoming loosenedfrom the backing sheet. were graded good, while those withstanding less than 50 were graded poor. The absence of a grade here and elsewhere indicates that the test was not performed.

Sheets withstanding 100 or more writings EXAMPLES XXI-XXV To determine the eiiect of variations in the amount of plasticizer, the following compositions were prepared, containing from 020% plasticizer of the combined weight of resin and plasticizer:

These compositions were coated on base sheets as in the prcccdin series of experiments summarized in the tables and, after aging for one Week, were tested for impression characteristics as before. he noted in write-off, i.e. density of impression, durability, i.e. number of possible impressions, or bleed.

No significant differencecould The following two examples illustrate the application of the invention to a two-sheet color developing transfer system.

EXAMPLE XXVI An emulsion of the following ingredients was prepared as in previous examples:

Material: Parts Pliolite NR resin 40 Santicizer 1H Santicizer S p-Phenyl leuco auramine Troluoil solvent 150 This emulsion was coated on 15 lb. tissue and dried to give a coating Weight of 10-12 pounds, 20" X 30"590 sheet ream. 7.5

By repetitive placing together of the colorless multicopy transfer sheet prepared above and a copy sheet having an attapulgite clay-containing receiving surface prepared as disclosed in US. Patent 2,548,366, and applying marking pressure, a number of receiving sheets developing a bright blue image of the written message were obtained.

EXAMPLE XXVII An emulsion of the following ingredients was prepared as in previous examples:

Material: 1 Parts Pliolite'NR'resin 4Q Santicizer 1H 2 Santicizer 8 -1 100 Tannic acid'- -c 10 Troluoil solvents 150 This emulsion was coated on 15 lb.- tissue (transfer sheet) and dried to give a coating weight of 12 pounds, 580 sheet (20" x 30) ream.

A copy receiving sheet for this transfer sheet was prepared by emulsifying a'solutionof 5 parts p-phenyl leuco auramine in parts second. mineral oil into 200 parts Water containing 5% polyvinylalcohol. This emulsion wascoated onto a 15 lb. clay coated sheet to give a dry deposit weight of 0.5 to 1 lb. per 20" X 30"500 sheet ream. When manifolded as in Example YXVI and marked, the copy sheets took on legible coloration corresponding to the marking.

The following is an example of the use of a solid pigment as the colorant:

EXAMPLE XXVIII An emulsion was prepared of the following ingredients:

Material: Parts Carbolac II pigment a carbon black having asurface arca of 850 sq.m.'/gm'. and of a particle diameter of 12 millimicrons from-G. -L.

Cabot) 30 Santicizer 8 Alpex resin 50 Dioctyl adipate 4 Troluoil solvent This emulsion was produced by grinding the pigment into the Santicizer 8 on a 3-roller mill to form a paste and dispersing the paste thus formed into a solution of the resin and plasticizer in the solvent. The dispersion was coated onto a 15 lb. carbonizing tissue at a weight of 12 lbs. (dry basis) per ream. While the performance of the sheet thus prepared did not equal the results obtained with comparable coatings containing a soluble dye, particularly as regards the durability of the sheet and the density of the copy impression, it was nevertheless capable of use in a plurality of transfer operations, producing visible impressions.

The term consisting essentially of is used herein in the definition of the ingredients whose presence in the claimed composition is essential, and as used it is intended to exclude the presence of other materials in such amounts as to interfere substantially with the properties and characteristics possessed by the composition set forth but to permit the presence of other materials in such amounts as not substantially to affect said properties and characteristics adversely.

Having thus described my invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A composition of matter adapted for use as a transfer coating upon a base sheet, said composition comprising a marking fluid homogeneously dispersed in the form of small droplets having an average diameter of less than about 20 microns throughout a solution of a film-former in a volatile aliphatic hydrocarbon solvent, said fluid and said film-former being present in proportions by weight having a ratio of about 1:3 to about 3:1, the combined amount of said film-former and said solvent being in excess of the amount of marking fluid so as to constitute a continuous phase, said film-former consisting essentially of a cyclized rubber resin, and said marking fluid consisting essentially by weight of about 10-30% of a colorant material and about 70-90% of a substantially non-volatile liquid colorant vehicle immiscible with said solvent, through which vehicle said colorant material is uniforrnly distributed.

2. The composition of claim 1 wherein th eratio of the proportion by weight of marking fluid to film-former is within the range of about 45/55 to about 70/30, and the amount of colorant in said marking fluid is at least about 20% by weight.

3. The composition of claim 1 wherein said solvent is present in the amount of 30-60%' by weight of the entire composition.

4. The composition of claim 3 wherein each of said resin and said marking fluid are present in an amount of about 10-52.5% by weight of the composition.

5. The composition of claim 1 wherein up to about 20% by weight of the cyclized rubber resin in said filmformer is replaced with a plasticizer for said resin.

6. The composition of claim 1 wherein said colorant vehicle is a substantially water-insoluble liquid selected from the group consisting of a polyepichlorohydrin having terminal hydroxyl groups and a N-ethyl toluene sulfonamide and said colorant is a dye soluble in said liquid selected from the group consisting of colored dyes and colorless intermediate forms of said dyes.

7. The composition of claim 5 wherein said colorant is substantially water-insoluble.

8. The composition of claim 6 wherein up to about 50% by weight of said water-insoluble liquid is replaced with a lower alkyl phthalyl-lower alkyl glycolate.

9. A composition of matter adapted for use as a transfer coating comprising essentially about 1052.5% of a cyclized rubber resin, about 52.5-10% of a marking fluid, and about 30-60% of a volatile aliphatic hydrocarbon solvent, said resin and said fluid being present by weight in the ratio of about 1:3 to about 3 1, said resin being dissolved in said solvent and constituting a contin- 18 nous phase in which said marking fluid is dispersed, said marking fluid being comprised essentially of about 70- 90% of a substantially non-volative liquid immiscible with said solvent and from about 10-30% of a colorant material uniformly distributed within said liquid, said marking fluid being dispersed homogeneously throughout said continuous phase in the form of small droplets having an average diameter of less than about 20 microns, all percentages being by weight.

10. A transfer sheet comprising a base sheet coated on at least one face thereof with a pressure-rupturable continuous film of a film-former consisting essentially by weight of a cyclized rubber resin, said film having homogeneously dispersed therethrough globules of a marking fluid having an average diameter of less than about 20 microns, the total weight of said fluid having a ratio to the weight of said film-former within the range of about 1:3 to about 3zl, said marking fluid being comprised essentially of about 10-30% by weight of a colorant and the remainder a liquid carrier for said colorant, said carrier being an essentially non-volatile liquid in which said resin is substantially non-soluble.

11. A transfer sheet as in claim 10 wherein the weight of said coating applied to each such face of said sheet is within the approximate range of 001-01 oz./sq. ft.

12. A transfer sheet as in claim 10 wherein said marking fluid constitutes about 45-70% of the weight of said coating and said film-former about 55-30% by weight of said coating.

13. A transfer sheet as in claim 10 wherein said filmformer consists essentially by weight of about -100% of said resin and up to about 20% of a plasticizer for said resin.

14. A transfer sheet as in claim 10 wherein said liquid carrier is a substantially water-insoluble liquid selected from the group consisting of a polyepichlorohydrin having terminal hydroxyl groups and a N-ethyl toluene sulfonamide.

15. A transfer sheet as in claim 14 wherein said colorant is a colored dye soluble in said liquid carrier.

16. A transfer sheet as in claim 14 wherein said colorant is a colorless intermediate form of a colored dye, which intermediate form is soluble in said liquid carrier, and said sheet is adapted for use with a copy sheet provided on its face with a compound reacting on contact with said intermediate form to convert the same to a colored dye.

17. A transfer sheet as in claim 10 wherein said colorant constitutes at least about 20% by weight of said marking fluid.

18. A transfer sheet as in claim 10 wherein said colorant is at least substantially water-insoluble.

19. A composition of matter adapted for use as a transfer coating upon a base sheet, said composition comprising a discontinuous phase of a marking fluid in a continuous phase of a solution of a film-former in a volatile solvent therefor, said fluid and said film-former being present in proportions by weight having a ratio of about 1:3 to about 3:1, said film-former consisting essentially by weight of a cyclized rubber resin, and said marking fluid consisting essentially by weight of about 10- 30% of a colorant material and about 70-90% of a substantially non-volatile liquid colorant vehicle immiscible with said solvent.

20. The composition of claim 19 wherein up to about 20% by weight of the cyclized rubber resin in said filmforrner is replaced with a plasticizer for said resin.

21. A transfer sheet comprising a base sheet coated on at least one face thereof with a pressure-rupturable continuous film of a film-former comprised essentially by weight by a cyclized rubber resin, said film containing a homogeneous discontinuous phase of a marking fluid, the weight of said marking fluid having a ratio to the 19 weight of said film-formerwithin the ranges of about 1:3 to about 3:1, said marking fluid being comprised essenti'ally of about 1030% by Weight of a colorant and the' remainder a liquid carrier for said colorant, said carrier being an essentially non-volatile liquid in which said resin is substantially non-soluble.

22. A transfer sheet as in claim 21 wherein up to about 20% by weight of the cyelized rubber resin is replaced with a plasticizer for said resin.

- UNITED STATES PATENTS Endres Aug. 25, 1936 Forman s Dec.,9, 1941 Clark July 5, 1960 FOREIGN PATENTS Germany Feb. 14, 1931 

10. A TRANSFER SHEET COMPRISING A BASE SHEET COATED ON AT LEAST ONE FACE THEREOF WITH A PRESSURE-RUPTURABLE CONTINUOUS FILM OF A FILM-FORMER CONSISTING ESSENTIALLY BY WEIGHT OF A CYCLIZED RUBBER RESIN, SAID FILM HAVING HOMOGENEOUSLY DISPERSED THRETHROUGH GLOBULES OF A MARKING FLUID HAVING AN AVERAGE DIAMETER OF LESS THAN ABOUT 20 MICRONS, THE TOTAL WEIGHT OF SAID FLUID HAVING A RATIO TO THE WEIGHT OF SAID FILM-FORMER WITHIN THE RANGE OF ABOUT 1:3 TO ABOUT 3:1, SAID MARKING FLUID BEING COMPRISED ESSENTIALLY OF ABOUT 10-30% BY WEIGHT OF A COLORANT AND THE REMAINDER OF A LIQUID CARRIER FOR SAID COLORANT, SAID CARRIER BEING AN ESSENTIALLY NON-VOLATILE LIQUID IN WHICH SAID RESIN IS SUBSTANTIALLY NON-SOLUBLE. 